CVE-2025-35939
CVE-2025-35939 is a security flaw in Craft CMS, software for building and running websites. Attackers are using a flaw in Craft CMS. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 2 Jun 2025.[1]
Craft CMS is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 5.7.5 and 4.15.3 of CMS.
Description
CISA calls it an external control of assumed-immutable web parameter in Craft CMS Craft CMS. In its words: “Craft CMS contains an external control of assumed-immutable web parameter vulnerability. This vulnerability could allow an unauthenticated client to introduce arbitrary values, such as PHP code, to a known local file location on the server. This vulnerability could be chained with CVE-2024-58136 as represented by CVE-2025-32432.”[1]
The CVE record adds: “Craft CMS stores arbitrary content provided by unauthenticated users in session files. This content could be accessed and executed, possibly using an independent vulnerability. Craft CMS redirects requests that require authentication to the login page and generates a session file on the server at '/var/lib/php/sessions'. Such session files are named 'sess_[session_value]', where '[session_value]' is provided to the client in a 'Set-Cookie' response header. Craft CMS stores the return URL requested by the client without sanitizing parameters. Consequently, an unauthenticated client can introduce arbitrary values, such as PHP code, to a known local file location on the server. Craft CMS versions 5.7.5 and 4.15.3 have been released to address this issue.”[2]
The underlying weakness is CWE-472, in MITRE’s list of common software weaknesses.
It scores 5.3 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| CMS | 5.7.5 |
| CMS | 4.15.3 |
Most families won’t have Craft CMS; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 2 Jun 2025, 26 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 23 Jun 2025 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 1%. That’s in the top 29% of the flaws it scores.[3]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
CISA’s required action: “Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Craft CMS is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 5.7.5 and 4.15.3 of CMS), or not in use. CISA gave US government agencies until 23 Jun 2025 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 5.3.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 1%.[3] |
See also
Other Craft CMS flaws
- CVE-2025-32432: code injection ·
- CVE-2024-56145: code injection ·
- CVE-2025-23209: code injection ·
Added the same day
- CVE-2025-3935, ConnectWise ScreenConnect: improper authentication ·
- CVE-2024-56145, Craft CMS: code injection ·
- CVE-2023-39780, ASUS RT-AX55 Routers: OS command injection ·
- CVE-2021-32030, ASUS Routers: improper authentication ·
Every Craft CMS flaw on CISA’s list · Everything added in June 2025
References
- ^ Cybersecurity and Infrastructure Security Agency. “Craft CMS External Control of Assumed-Immutable Web Parameter Vulnerability”. Known Exploited Vulnerabilities Catalog, added 2 Jun 2025.
- ^ National Institute of Standards and Technology. “CVE-2025-35939 Detail”. National Vulnerability Database, published 7 May 2025.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.013, percentile 71.5, 31 Oct 2026.
- CVE Program. “CVE-2025-35939”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.